One reason that has delayed widespread usage of Radio Frequency Identification (RFID) tags is cost. Typical application areas of RFID tags include recycle monitoring, security printing, underground pipes distinguishing and ticket identification that may not be able to use barcodes. In comparison to RFID tags, the barcode system is relatively mature, and more importantly, the cost of a barcode is nearly zero. Unlike a barcode, a chipless RFID tag contains bits of data that can be quietly and electronically detected at a distance even if it is not visible. Problems of orientation and obscuration are no longer a problem. The key criticism of chipless RFID tags is that they do not provide remote rewritable capability. But this is not always a problem as modern networks can facilitate the management of all information centrally and an ID/serial number is adequate enough to serve as the only key to retrieve the required information through the network. In fact, chipless tags with fixed data have proven to be more robust than those with rewritable capability. A read only device is electronically addressed more securely, more reliably, less costly and longer operating range than a read-write device.
Chipless RFID tags are widely used in the identification of goods and logistics tracking. Their principle of operation has several variations. U.S. Pat. No. 6,966,493 discloses a Surface Acoustic Wave (SAW) device that works on the principle of a surface acoustic wave traveling along the surface of some piezoelectric materials and the resonance generated thereof with metallization on surface generates different frequencies of electromagnetic waves and is transmitted back to receivers at different time intervals. Such an arrangement suffers from the restricted angle of incident of the radio wave.
Therefore, it is desirable to provide a tag that is relatively inexpensive to manufacture, has a small form factor and is more effective and accurate than some prior art tags used for identification.